Method and means for producing a low energy detonator



June 1961 R. H. F. STRESAU ETAL 2,986,803

METHOD AND MEANS FOR PRODUCING A LOW ENERGY DETONATOR 4 Sheets-Sheet 1Filed Jan. 6, 1949 gvvumn bo'w R. H. E STRESAU H. J. PLUMLEY R. H. F.STRESAU ET AL June 6, 1961 METHOD AND MEANS FOR PRODUCING A LOW ENERGYDETONATOR Filed Jan. 6, 1949 4 Shee ts-Shee N @NE e/wton R. H. F STRESH. J PLUMLEY June 6, R, H. F, STRESAU ETAL METHOD AND MEANS FORPRODUCING A LOW ENERGY DETONATOR 4 Sheets-Sheet 3 Filed Jan. 6, 1949awe/whoa R. H. E STRESAU H. J. PLUMLEY W June 6, 1961 R. H. F. STRESAUET AL METHOD AND MEANS FOR PRODUCING A LOW ENERGY DETONATOR Filed Jan.6, 1949 4 Sheets-Sheet 4 Elma/whom R. H. F. STRESAU H. J. PLUMLEY METHODAND MEANS FOR PRODUCING A LOW ENERGY DETONATOR Richard H. F. Stresau,Washington Grove, Md., and

Harold J. Plumley, Washington, D.C.

Filed Jan. 6, 1949, Ser. No. 69,547 20 Claims. (Cl. 29155.5) (Grantedunder Title 35, U.S. Code (1952), sec. 266) This invention relates to anelectrical initiator for a detonator and more particularly to anapparatus for constructing and applying a low energy operated initiatorto the end f a wire bridge type of detonator plug. The present inventionprovides a new and improved method and apparatus for securing arelatively fine wire or initiator to the end of a detonator plug byspraying molten metal thereon in which the bridge portion of theinitiator 1s maintained at a predetermined effective length during theaforesaid spraying operation.

The invention further provides a method and apparatus for applying aninitiator wire of relatively small diameter to the detonator plug insuch a manner that only a small portion of the initiator wire iseifective'to ignite the exlplosive in response to an electrical impulsereceived there- One of the objects of the invention is the provision ofa new and improved method and apparatus whereby an electrical initiatoris applied and secured to a chemically treated end of the detonatorplug. I

Another object of the invention is the provision of a new and improvedapparatus for applying and securing a length of fine initiator wire tothe detonator plug.

A further object of the invention is the provision of a new and improveddevice for controlling the effective length of the bridge portion of afine wire initiator for a low energy detonator as the initiator issecured to the end of the detonator plug.

Other objects and many of this invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein: I

the attendant advantages of FIG. 1 is a plan view of the device of thepresent invention and showing portions thereof broken away and insection;

FIG. 2 is an elevational view of the device of FIG. 1 and showingportions of the device broken away and in section; v I

FIG. 3 is an enlarged fragmentary sectional view of the device of FIG. 1and showing a detonator plug arranged therein, before the top plateassembly supporting a length of initiating wire has been clamped to theplug holder assembly;

FIG. 4 is a view similar to FIG. 3 but showing the top plate ina clampedcondition with respect to the plug holder and the initiating wireembedded in the end of the detonator plug; I

FIG. 5 is a detail sectional view taken on the line 55 of FIG. 3;

FIG. 6 is a diagrammatical view showing an arrangement whereby theinitiating wire is secured to the end of the detonator plug by sprayingthe end of the plug with molten metal;

FIG. 7 is an enlarged sectional view of the top plate assembly and takenon the line 7--7 of FIG. 2;

\FIG. 8 is a view similar to FIG. 7 but taken on the line 8-8 of FIG. 2;

FIG. 9 is an enlarged end view of the detonator 'plug and the finebridge wire initiator secured thereto;

FIG. 10 is a fragmentary sectional view taken on the line 10-10 of FIG.9;

2,986,803 Patented June 6, 1961 FIG. 11 is a sectional view taken on theline 1111 of FIG. 10; and

FIG. 12 is an enlarged sectional view of a complete detonator andinitiator therefor.

Referring now to the drawings for a complete understanding of theinvention and more particularly to FIGS. 1 and 2, the device forapplying the initiator wire to a detonator plug is generally indicatedby the reference character 10, and comprises an elongated base orsupporting member 11, composed of any material suitable for the purposesuch, for example, as laminated Bakelite. The member 11 is provided witha plurality of bores 12 extending therethrough for slideably supportinga plurality of plug holders generally indicated by the numeral 13 andrespectively arranged in bores 12, each plug holder comprising a shaft14 respectively extending through bearings 20 formed in the member 11,and having a knurled knob 17 arranged on one end thereof and a head 18adjustably secured to the other end as by threaded engage menttherewith, the head 18 being provided with a transversely arranged slot19, FIGS. 3, 4 and 5. As shown on FIGS. 1 and 2, rotative movement ofthe heads 18 is prevented with respect to the shafts 14 by a pluralityof screws and keyways respectively disposed in the member 11 and heads18, indicated by the numerals 21 and 22. It will be understood, however,that upon rotation of the knobs 17 the heads 18 will be slideablyadjusted within the bores 12 by reason of the threaded connectionbetween the shafts 14 and bores 23 formed in the heads 18. Surroundingthe shafts 14 and having one end thereof in abutting engagement with theheads 18 respectively and the other end in abutting engagement with thebearings 20 respectively is a spring 24. By this arrangement thedetonator plugs generally indicated by the numeral 26 are adjustablymaintained in the desired position within the member 11, with thereduced end 27 on each plug extending a predetermined amount beyond theouter surface of member 11 such, for example, as .020 of an inch. Eachplug is provided with a pair of spaced terminals 28 molded therein andextending therefrom, the terminals on each plug being respectivelydisposed within the slots 19 in heads 18 when the device is assembledand thus the plugs are maintained within the bores 12 in desiredrelation with respect to each other whereby the terminals on the plugsare in alignment as most clearly shown on FIG. 1.

In preparing each plug prior to the fabrication operation, the surface31 thereof is ground, whereupon the plug is further prepared by etchingthe ground surface in an alkaline solution such, for example, as a 10%aqueous solution of potassium hydroxide. The etching operation iscontinued until the ground surface of the plug is rough and soft enoughto assure a good adherent surface. When this has been done the plugs arearranged within the member or base 11 in the aforesaid manner with thereduced ends 27 thereof extending beyond the outer surface of the memberwhereupon the surface 31 of each plug is wiped with a cloth containing acopious amount of carbon tetrachloride, thus removing fingerprints,grease and dirt therefrom.

The initiator wire 30 comprising the bridge of the detonator plug isdrawn very fine and etched, a wire having a diameter of .0001 to .00045inch having been found satisfactory for the purpose. In applying theinitiator wire 30 to the heretofore mentioned end portion of the plugs,a top plate assembly generally indicated by the reference character 32is employed as more clearly shown in FIGS. 2, 7 and 8. The plateassembly comprises an elongated member 33, composed of any materialsuitable for the purpose such, for example, as steel and having aplurality of blocks 34 secured thereto as by screws 35 or the like, theinitiator wire 30 being secured to and along 3. a common centerline ofthe under surface of the block assembly as by Scotch tape 36, FIGS. 1and 2. Arranged between each block and in engagementtherewith is a shim37. The blocks are provided With arcu'ate notches respectively formed inthe outer surfaces thereof and arranged in such a manner as to form aplurality of holes 38 therebetween when the blocks are assembled, eachhole being bisected by one of the shims 37 and in registration with acomplementary bore 39 formed in member 33, the bores 39 terminating at awall defining the bottom surface of a groove or guideway 41, FIGS. 1, 7and 8. As more clearly shown on FIG. 1 the blocks and shims are securedtogether and drawn into abutting engagement with respect to each otherby a pair of bolts indicated by the reference character '40, one endthereof being respectively threaded into bores arranged in the end blockof the block assembly, the other end of each bolt having an enlargedhead thereon and in abutting engagement with the outer surface of theother end block of the block assembly. As hereinbefore described theblocks are secured to the member 33 by screws 35. To provide a unitarytop plate assembly after the blocks, shims and members have beenassembled in the aforesaid manner, the shims are .Welded to the blocks34 as at 50 and the member 33 is welded to the blocks as at 60, FIGS. 7and 8. As shown more clearly on FIGS. 1 and 2 the top plate assembly 32is guided into proper position with respect to member 11 by a pair ofdowel pins 42, supported thereby and adapted respectively to engage a'pair of openings 43 formed in the plate assembly 32 and thus the shimsare positioned at a right angle with respect to the common centerline ofthe top plate assembly and the initiator wire coincides therewith, theshims and wire intersecting at a point, FIG. 1. By reason of theaforesaid arrangement a portion of the ground and etched surface of eachplug 26 is masked corresponding to the thickness of the respective shimsthereforand the effective portion of the initiator wire 30 in alignmentwith the ends of each plug is also masked by the shims.

The length of this unmasked bridge portion is only sufiicient to causethe fine wire bridge to be heated to incande'scence in'response to themomentary application of electrical energy in the order of 50 ergsapplied thereto from a suitable source such, for "example, as thevoltage generating devices disclosed and claimed in the copendingapplication of Harold J. Plumley for Magnetic Inertia Controlled Fuze,Serial No. 535,799, filed May 16', 1944,

now Patent 2,848,948. To achieve this result it is necesthe member 11 itis clamped in position thereon by a pair of clamping devices 45respectively disposed on the ends thereof and comprising a'pair of clampplates 46 maintained in clamping engagement withrespect to-the plateassembly by a pair of bolts 47 and wing nuts 48, FIGS;

land 2. When this has been done the wire 30'is forced into the groundand etched surfaces of each plug by the aforesaid spring and plug holderarrangement associated therewith, the prongs of eachplug respectivelyextending into the slots 13 in heads 18. When the aforesaidclampingoperation has been completed the initiator wire is secured to the groundand etched end of the battery of plugs arranged therein in the followingmanner.

With particular reference to FIG. 6 the assembly 32 is supported in anysuitable manner adjacent a metal spray gun 49 with the grooved surface41 thereof outermost and in alignment with the gun nozzle '51, suchthatthe molten metal sprayed therefrom is directed into the aforesaid holesor openings 38 and 39 formed in the plate assembly 32 onto the groundand etched end of the plugs and thus securing of the wire to the plugsin electrical connection with the prongs is accomplished. It has beenfound that during the spraying operation the best results are obtainedwhen the' discharge end of the nozzle is spaced substantially threeinches from the work. It will be understood, however, that any means maybe employed for supporting the spray gun in operative relation withrespect to'the work which permits transverse movement thereof withrespect thereto, such for example as a lathe generally indicated by thenumeral 52, FIG. 6, the gun being secured to the movable carriagethereof by the tool post 53. It has further been found that the bestspraying results are obtained when the traversing speed of the carriageto which the gun is secured is between 13 to 26 inches per minute andthe spray wire 54 on reel 55 is automatically fed therefrom through therear end of the gun in the usual manner in solid condition anddischarged from the nozzle end 51 thereof into the aforesaid groove in asprayed molten condition, the wire being composed of any suitablematerial for the purpose such, for example, as silver solder, brass,copper or the like.

The spray gun is provided with the usual three way valve 56 adapted tobe adjusted in such a manner as to provide a suflicient amount of air,gas and oxygen pressure to cause proper combustion and sufiicient heattherefrom; at the'nozz le end of the gun to melt the wire as the wire isfed therethrough in the usual manner, the air, gas and oxygenconnections to the valve being indicated by the reference characters 57,58 and 59.

After the spraying operation has been completed, the clamp devices 45are released from clamping engagement with member 11 whereupon the topplate assembly is rocked sufi'lciently transversely to free it from themetal spray. When this has been accomplished the Scotch tape is removedfrom the top plate assembly and the plate removed from the member 11thereby exposing the fabricated ends of each plug with the initiatorwire 30 embedded therein by -the spray metal 60 except for the portionsthereof respectively masked by the shims, it being understood, that thesurplus portions of the wire be tween each of the plugs not coated bythe spray operation is removed in any suitable manner preferably bycutting the wire on opposite sides of each of the plugs therebyproviding an initiator 61 having a relative small bridge portion 62.When the cutting operation has been completed the plugs are readilyremoved from the member 11 by moving the plugs outwardly a predeterminedamount beyond the outer surface of the member 11 by the aforesaid plugholder and spring arrangement respectively associated therewith afterthe plate assembly has been removed from the member 11;

In preparing the portion 27of the plug prior to securing the explosivecap 63 thereto, FIG. 12, it .is essential to chamfer or bevel the endportion of the plug including the spray metal 60 thereon as indicated at64, FIGS. 10 and 11. When thislhas been-done the cap is secured to theportion 27 of the plug as by 'a pressfit therewith, FIG. 12, and, dueto-the beveled portion thereof and by reason of the insulating washer 65disposed within the cap and forced into engagement with the aforesaidspray metal 60 as the cap is pressed on portion 27, the possibility of ashort circuit occurring between the aforesaid parts is eliminated.

The cap 63 is composed ofany material suitable for the purpose such, forexample, as aluminum, the cap having a bore 66 arranged therein.Disposed within the bore 66 and surrounding the bridge 62 is anexplosive charge 67 suitable for the purpose such, for example, 'as leadazide 'or the like, FIG. '12. It will be understood, however, that anysuitable method maybe employed for loading the :c'ap with the aforesaidexplosive such, for example, as pressing the explosive into the hereunder a predetermined {amount ofpressure.

From the foregoing description it will be apparent that a device andmethod is provided for applying and securguesses ing an electricalinitiator of low impedance and low energy requirement to a detonatorplug, in which the securing of the initiator to the end of a detonatorplug is accomplished by spraying the end thereof with molten metal insuch a manner as to cover the end of the plug and initiator except for anarrow strip masked by the edge of a relatively thin shim, and thusfacilitating the application of a wire of small diameter to the end of adetonator plug and also controlling the effective length or bridgeportion thereof whereby the low energy required to cause firing thereofis concentrated on a small quantity of the material comprising theinitiator.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. In an apparatus for applying a fine electrical initiator wire to anexposed end of a plurality of detonator plugs and in bonded relationwith a pair of terminals arranged within each of said plugs, a basemember for supporting said detonator plugs in spaced relation withrespect to each other, means detachably secured to said base member forsupporting a length of said wire thereon, said wire being adapted tointersect said exposed end of the plugs and said terminals at the centerpoints thereof when the supporting means is secured to the base member,and a plurality of elements secured to the supporting means andrespectively bisecting said exposed ends of the plugs at a right anglewith respect to said wire for masking a portion of the wire and the endof each plug sufliciently to form a minute bridge portion thereon asmolten metal is sprayed upon the exposed end of the plugs and on theterminals.

2. In an apparatus for applying a fine electrical initiator wire to anexposed end of a plurality of detonator plugs and in bonded relationwith a pair of terminals arranged within each of said plugs, a basemember, means for slidably supporting said plugs within said base memberin predetermined spaced relation with respect to each other, meansdetachably secured to said base member for supporting a length of saidwire thereon, said wire being adapted to intersect said exposed end ofthe plugs and said terminals at the center points thereof when thesupporting means is secured to said base member, means on said plugsupporting means for maintaining said exposed ends of the plugs and theterminals in engagement with said wire, and a plurality of elementssecured to said supporting means and respectively bisecting the exposedends of the plugs for masking a portion of the wire and of said end ofeach plug sufliciently to form a minute bridge portion thereon as moltenmetal is sprayed thereon and on the terminals.

3. In an apparatus for applying an electrical initiator to an exposedend of a plurality of detonator plugs and in bonded relation with a pairof terminals arranged Within each of said plugs and in face adjacencywith respect thereto, a base member having a plurality of spaced boresextending therethrough, a plurality of actuating plungers slidablydisposed within said bores respectively for supporting the plugstherein, a plate clamped to the base member and having a plurality ofspaced openings extending therethrough and in registration with saidbores, means for clamping said plate to the base member, a length offine wire secured to said plate and adapted to intersect the bores,openings, and said pair of terminals at the center points thereof whenthe plate is clamped to the base member, means on the plungers forforcibly urging said end of the plugs and the terminals therein intoengagement with said Wire when the bores and openings are inregistration and the plate is clamped to the base member, and aplurality of'elements secured to the platefand respectively bisectingthe openings therein for masking a portion of the wire'and of said endof the plugssufficiently to form a minute bridge portion thereon asmolten metal is sprayed into the openings and upon the exposed ends ofthe plugs and the terminals.

4. In an apparatus for applying an electrical initiator to an exposedend of a plurality of detonator plugs and in bonded relation with a pairof terminals arranged within each of said plugs, a base member, saidbase member having a plurality of spaced bores extending therethrough, aplurality of actuating plungers slidably disposed within said boresrespectively, means on said plungers for supporting the plugs thereon, aplate detachably clamped to the base member and having a plurality ofopenings extending therethrough and in registration with the boresrespectively, means for clamping said plate to the base member, a lengthof fine wire secured to said plate and adapted to intersect the bores,openings and said terminals in the plugs at the center points thereofwhen the plate is clamped to the base member, means on the plungers forforcibly urging said end of the plugs and the terminals therein intoengagement with said wire when the bores and openings are in saidregistration andthe plate is clamped to the base member, and a pluralityof elements secured to the plate and respectively bisecting saidopenings therein and the bores in the base member for masking a portionof the wire and of said end of the plugs sufliciently to form a minutebridge portion thereon as molten metal is sprayed into the openings andupon the exposed end of the plugs and on the terminals.

5. In an apparatus for applying an electrical initiator to an exposedend of a plurality of detonator plugs, a base member having a pluralityof spaced bores extending therethrough, a plurality of plugsrespectively disposed Within said bores, each plug having a pair ofterminals disposed therein and extending therethrough, a plurality ofactuating plungers slideably disposed within said bores respectively,means on each plunger and in engagement with said pair of terminals oneach plug for supporting the plugs, a plate having a plurality of spacedopenings extending therethrough and in registration with said bores whenthe plate is clamped to the base member, means for clamping said plateto the base member, a length of fine wire secured to the plate,resilient means disposed on the plungers for forcibly urging said endsof the plugs and the pair of terminals respectively disposed thereininto engagement with said wire when the plate is clamped to the basemember, and means secured to the plate and respectively bisecting theopenings therein and the bores in the base member for masking a portionof the wire and of said end of the plugs sufiiciently to form a minutebridge port-ion thereon as molten metal is sprayed into the openings andupon the exposed ends of the plugs and the terminals.

6. In an apparatus for applying an electrical initiator to one end of abattery of detonator plugs and in bonded relation with a pair ofterminals disposed therein and extending through each of said plugs, abase member having a plurality of spaced bores extending therethrough, aplurality of plungers slideably arranged within said bores respectively,means including a slot arranged in each of said plungers and inengagement with said pair of term-inals for supporting one of said plugsthereon and within the bores respectively, a plate detachably clamped tosaid base member and having a plurality of spaced openings therein inregistration with said bores, a length of fine wire secured to saidplate and respectively intersecting the exposed end of the plugs, andmeans including a plurality of members-secured to said base member andbisecting said bores and openings for masking a portion of the wire andof the end of the plugs sufliciently to form a minute bridge portionthereon as molten metal is sprayed into said openings and upon theexposed ends of the plugs and the terminals.

7. In an apparatus for applying an electrical initiator to an exposedend of 'a plurality of detonator plugs and in bonded relation with apair of spaced terminals disposed within and extending through each ofsaid plugs, a base member, said base member having a plurality of spacedbores extending therethrough, a plurality of plungers slideably arrangedwithin said bores respectively for supporting said plugs, meansincluding a plurality of slots arranged in the plungers for respectivelyreceiving a pair of said terminals thereby to prevent rotation of theplugs Within the bores, a plate having a plurality of spaced openingsextending therethrough and in registration with said spaced boresrespectively when the plate is clamped to said base member, means fordetachably clamping said plate to the base member, a length of fine wiresecured to said plate, resilient means arranged in each of the bores andin abutting engagement with the plungers therein for forcibly urgingsaid end'of the plugs and said terminals into engagement with said wirewhen the plate is clamped to the base member, and a plurality ofelongated devices secured to the plate and bisecting the openingstherein and said bores for masking a portion of the wire and of said endof the plugs sufliciently to form a minute bridge portion thereon asmolten metal is sprayed into the openings and upon the exposed ends ofthe plugs and the terminals.

8. In an apparatus for applying an electrical initiator to one end of abattery of detonator plugs and in bonded relation with a plurality ofterminals arranged in pairs, each of said pairs being disposed within aplug and extending therethrough, a base member having a plurality ofspaced bores extending therethrough, a plurality of plungers slideablyarranged within said bores respectively, means on said plungers and inengagement with a pair of said terminals for supporting the plugsthereon and within said bores respectively, a plate detachably clampedto said base member and having a plurality of spaced openings therein inrespective registration with said bores, a plurality of complementarymembers secured in closely spaced alinement to said plate, each of saidmembers having an arcuate notch provided therein in registration withrespect to the notch of an adjacent member whereby said notches arealined with said bores and openings, a length of fine Wire secured tosaid members, and a plurality 'of devices disposed between each of saidcomplementary members adjacent said notches and bisecting the bores andopenings for masking a portion of the Wire and of said end of the plugssufiiciently to form a minute bridge portion thereon as molten metal issprayed into the opening and upon the exposed ends of the plugs and theterminals.

9. A device for applying a fine electrical initiator wire to an exposedend of a detonator plug and in bonded relation with a pair ofterminalsdisposed therein and extending therethrough, a base member, meansincluding said terminals for supporting the plug within said base memberand in engagement with said initiator wire, and means bisecting said endof the plug at a right angle with respect to the initiator wire formasking a portion of the wire and of said end of the plug sufiicientlyto form a minute bridge portion on the initiator wire as molten metal issprayed upon the end of the plug and on the terminals.

10. A method of securing a low energy fine wire initiator to the end ofa detonator plug and to a pair of spaced terminals disposed thereinwhich comprises etching said end of the plug sufficiently to produce anadherent surface thereon, applying a length of said wire to said end ofthe plug and to the terminals, masking a portion of the etched end ofthe plug and a minute portion of said wi-re intermediate the terminals,and thereafter spraying the unmasked portion of the etched "end of theplug, the

wire and the terminals with molten metal sufficiently to secure the wireto the plug and to the terminals.

11. A method of securing a low energy fine wire initiator to the end ofa detonator plug and to a pair of spaced terminals disposed thereinwhich comprises etching said end of the, plug with a 10% aqueoussolution of potassium hydroxide sufilciently to produce an adherentsurface thereon, applying a length of said Wire to the end of the plugand to the terminals, masking a portion of the etched end of the plugand a minute portion of the wire intermediate the terminals, applyingforce to the plug sufficient to cause the wire, to be embedded in saidetched end and to engage the terminals, and thereafter spraying theunmasked portion of the etched end of the plug, the terminals and thewire with molten metal.

12. A method of securing a low energy fine wire initiator to the exposedend of a detonator plug and to a pair of spaced terminals disposedtherein which oomprises etching said end of the plug with a 10% aqueoussolution of potassium hydroxide suificiently to produce an adherentsurface thereon, arranging said wire superficially with respect to saidexposed end of the plug and said terminals, masking a portion of saidetched end of the plug and a minute portion of said wire intermediatethe terminals, applying force to the plug sufiicient to cause the wireto be embedded in the etched end of the plug and engage the terminals,and thereafter spraying the unmasked portion of the etched end of theplug, the terminals and the Wire with molten metal.

13. A method of securing a low energy fine wire initiator to the exposedend of a detonator plug and a pair of spaced terminals disposed thereinwhich comprises etching said end of the plug with a 10% aqueous solutionof potassium hydroxide sufiiciently to produce an adherent surfacethereon, arranging said wire in such a manner as to intersect saidetched end of the plug and said pair of terminals, masking a portion ofthe etched end of the plug and a minute portion of the wire, applyingsulficient pressure to the plug to maintain the wire in engagement withsaid terminals and cause the wire to be embedded in the etched endthereof, and thereafter spraying the unmasked portion of the etched endof the plug, the terminals and the wire with molten metal.

14. A method of securing a low energy initiator wire to the exposed endof a plurality of detonator plugs and a pair of spaced terminalsrespectively disposed therein which comprises etching said end of eachplug sufiiciently to produce an adherent surface thereon, arranging alength of said wire in such a manner as to interswt said etched end ofthe plugs and said terminals, respectively masking a portion of each ofthe plugs and portions of said wire, and thereafter spraying theunmasked portion of the etched end of each plug, the terminals and thewire with molten metal.

15. A method of securing a length of fine initiator wire to the end of aplurality of detonator plugs and to a pair of spaced terminalsrespectively disposed therein which comprises etching one end of eachplug sufiicient- 1y to produce an adherent surface thereon, arrangingsaid wire in such a manner as to intersect the etched end of the plugsand said pair of terminals therein, masking a portion of each of theplugs and of the wire, applying sufficient pressure to the plugsrespectively to maintain the wire in engagement with said terminals andto cause a portion of the wire to be embedded in the etched end of theplugs, and spraying the portions of the etched end of each plug, theterminals and the Wire with molten metal.

'16. A method of securing a length of fine initiator wire to the end ofa plurality of plugs and to a pair of spaced terminals respectivelydisposed therein which comprises etching one end of each plug with a 10%aqueous solution of potassium hydroxide sufiiciently to produce anadherent surface thereon, arranging a length of said wire in such amanner as to respectively intersect the etched end of each plug and saidpair of terminals therein, respectively masking a fractional portion ofthe etched end of the plugs and of the wire intermediate said pair ofterminals, applying sufiicient pressure respectively to the plugs tocause a portion of the wire to be embedded in the etched ends thereofand in engagement with said pair of terminals, and spraying the unmaskedportion of the wire and of the etched ends of each plug including thepair of spaced terminals therein with molten metal.

17. An apparatus for securing a length of fine initiator wire to anetched end of a plurality of detonator plugs and to a pair of spacedterminals respectively disposed in said plugs which comprises meanssupporting the plugs with the etched end thereof exposed, meansarranging a length of initiator wire in such a manner as to intersectthe etched end of each plug and said pair of terminals therein, meansmasking a fractional portion of the etched end of the plugs and of thewire intermediate said pair of terminals, means applying sufiicientpressure to the plugs to cause a portion of the wire to be embedded inthe etched end thereof and in engagement with said pair of terminals,and means adapted to spray the unmasked portion of the wire and theetched end of each plug including the pair of spaced terminals thereinwith molten metal.

18. A method for securing a length of fine initiator wire to the end ofa plurality of plugs and to a pair of spaced terminals respectivelydisposed in said plugs which comprises etching one end of each plugsufiiciently to produce an adherent surface thereon, supporting the plugwith the etched end thereof exposed, arranging a length of initiatorwire in such a manner as to intersect the etched end of each plug andsaid pair of terminals therein, masking a fractional portion of theetched end of the plug and the wire intermediate said pair of terminals,applying sufiicient pressure to the plug to cause a portion of the wireto be embedded in the etched end thereof and in engagement with saidpair of terminals, and spraying the unmasked portion of the wire and theetched end of each plug including the pair of spaced terminals withmolten metal.

19. An apparatus for securing a length of fine initiator wire to anetched end of a plurality of detonator plugs and to a pair of spacedterminals disposed in said plugs which comprises means supporting theplugs with the etched end thereof exposed, means positioning a length ofinitiator wire in such a manner as to intersect the etched end of eachplug and said pair of terminals therein, means masking a fractionalportion of the etched end of the plug and of the wire intermediate saidpair of terminals and means situated to spray the unmasked portion ofthe wire and the etched end of each plug including the pair of spacedterminals therein with molten metal.

20. A method of securing a length of initiator wire to an etched end ofa plurality of detonator plugs and to a pair of spaced terminalsdisposed in said plugs which comprises supporting the plugs with theetched end thereof exposed, positioning a length of initiator wire insuch a manner as to intersect the etched end of each plug and said pairof terminals therein, masking a fractional portion of the etched end ofthe plug and the wire intermediate said pair of terminals, and sprayingthe unmasked portion of the wire and the etched end of each plugincluding the pair of spaced terminals therein with molten metal.

References Cited in the file of this patent UNITED STATES PATENTS1,612,479 Wellhauser Dec. 28, 1926 2,005,897 Knowles June 25, 19352,107,903 Peters Feb. 8, 1938 2,182,968 Lunsford Dec. 12, 1939 2,260,558Caughey Oct. 28, 1941 2,365,539 Flowers Dec. 19, 1944 2,387,083 McCainOct. 16, 1945 2,393,780 Johansson Jan. 29, 1946 2,445,874 De BoisblancJuly 27, 1948 2,466,890 Gilbertson Apr. 12, 1949 OTHER REFERENCES Steemagazine, September 15, 1947, pages 96 and article by Collier.

